Lighting fixtures or luminaires are typically made from cast aluminum housings. Cast aluminum housings are used to dissipate heat that is generated by the light source and the power supply to energize that source. In the case of light-emitting diode (LED) lighting fixtures, it is extremely important and imperative that the junction temperature of the LED is maintained within the temperatures that are reported in LM80 data supplied by the LED manufacturer. If the temperature is not maintained and exceeds the allowable threshold, the life of the LED diminishes substantially, the color characteristics can change, and the lumen output decreases.
Existing cast aluminum fixtures are a good solution for dissipating heat because aluminum has very good theimal conductive properties that transfer the heat away from the LED light engine to maintain a desired junction temperature of the LED. While this aluminum housing is good at heat dissipation, it is not very good at corrosion resistance, has design limitations, and is heavy. Poorly designed aluminum heat sink housings with the use of higher power LEDs can create many of these problems.
Corrosion is a significant issue and a problem for aluminum lighting fixtures. There have been advances made in coating aluminum fixtures to help against corrosion which include expensive multi-stage coatings but these are still susceptible to corrosion in environments that have salt and other types of chemicals and contaminants. These aluminum fixtures can easily deteriorate from both the outside due to the failure of the coating and the inside of the fixture which does not have a protective coating. Another disadvantage of the aluminum LED fixture housing is material cost and the need to perform secondary operations for assembly.
Thus, there is a need for a type of lighting fixture that is corrosion resistant inside and outside and yet solves the existing issues with aluminum LED fixtures including high cost and high weight.